Onera searches for peace and quiet

French aerospace research agency Onera (Stand A321) is exploring a new way to cut noise inside the cabin of an airplane. Researchers have used a principle that simply is the reverse of the usual one.

“We first defined the material that would best reduce the noise and then we synthesized it,” Michel de Gliniasty, Onera’s general scientific director, explained recently. The optimization process led to a particular structure, now patented and very efficient at low frequencies. The structure is called a periodic one because it repeats itself.

Steel panels using this structure and only two centimeters (0.79 inch) thick have been manufactured. They fit inside a large business jet’s fuselage, as an insulation blanket. The results are unexpectedly good, according to Onera researchers. For example, they have managed to cut the noise by 12 dB between 300 and 600 Hz.

The material is said to be the lightest available for this level of performance. Daniel Osmont, the Onera researcher who is leading the team in charge of the project, is now looking forward to using the same structure with other materials. Replacing steel with thicker composites would better absorb noise.